Air springs of the kind mentioned above cushion two parts that are moveable relative to each other and thus increase the suspension comfort of motor vehicles and driver's cabs. Conventional air springs have a rubber air spring bellows connected to a closure member most frequently configured as a lid and a rolling piston in order to form a working space sealed in an air-tight manner. The working space is filled with a fluid, in particular compressed air, as a working medium. During spring contraction and extension, the air spring bellows rolls on the outer surface of the rolling piston and thus cushions in vibrations that are introduced.
In addition to the above-described cushioning function, a damping function can also be integrated into an air spring. Such an air spring may also be referred to as an air spring damper. Damping most frequently takes place by the working medium flowing back and forth between the working space and another chamber via a damping channel. Due to the constricted cross section of the damping channel and the accompanying friction, the introduced vibrations are damped. Different damping characteristics can be set by varying the damping channel cross section.
Moreover, air springs are also used to keep a desired level position of a motor vehicle or of a driver's cab constant at different loads or weight loads, or to change it in adjustable manner. This is done by filling the working space with compressed air or by releasing compressed air from the working space. For this purpose, the working space is connected to a compressed-air control device that changes the spring stroke depending on the load state or the weight loads. Compressed air is most frequently filled in or released via control valves disposed outside the working chamber.
From DE 10 2011 108 249 A1, an air spring is known which has a mechanically operable control valve integrated into the air spring for controlling the level position of a motor vehicle or of a driver's cab. The control valve is mounted on the lid and comprises regulating valves for regulating the compressed-air supply or the compressed-air release. The pressure-regulating valves are actuated via cams attached to a rotatable camshaft. In the process, the rotary movement of the camshaft takes place via a drag lever, which rests with its free end on a contact surface on the rolling piston of the air spring. The camshaft is turned by the pivoting movement of the drag lever, whereby one of the cams, depending on the contraction or extension of the air spring, actuates one of the tappets of the regulating valves kept shut by spring forces.
Furthermore, an air spring assembly with an integrated valve control system for controlling the level position of a motor vehicle or of a driver's cab is presented by DE 10 2011 114 570 A1. The integrated valve control system comprises an air inlet valve and an air outlet valve disposed in the region of a lid. A compression spring assembly formed of two parts is provided for opening and closing the valves. The compression spring assembly has a central spring facing towards the rolling piston or the lid and a control valve biasing spring facing towards the air release valve. The central spring and the control valve biasing spring are disposed on a guide tube mounted in an axially freely movable manner between the rolling piston and the lid. A radially protruding stop, which serves as a control means for actuating the valve tappet of the inlet valve, is disposed between the two springs. The compression spring assembly is retained between biasing means, with one of the biasing means contacting the outlet valve. During spring contraction, the guide tube slides downwards, and at the same time, the control valve biasing spring is compressed until the stop contacts the inlet valve after covering a free distance and actuates it. During spring extension, the guide tube moves upwards, with the control valve biasing spring extending so that the biasing means associated with the outlet valve moves away from it and the outlet valve is opened.